The present invention relates to a new and improved process for the continuous bonding of staple fibers into an essentially non-twisted yarn and also concerns a new and improved yarn produced according to the aforesaid process.
The textile spinning art is already acquainted with the technique of imbuing a suitably prepared, non-twisted fiber arrangement formed of staple fibers with adhesive distributed in a liquid, squeezing-off the excess liquid while compacting the fiber arrangement at all sides in a pressure zone, and transforming the staple fibers compacted into a band into a yarn by setting the adhesive and drying by means of dry air.
When applying the liquid by means of a liquid applicator or liquid applying device, for instance of the type disclosed in my commonly assigned, copending United States Patent application Ser. No. 187,966, filed Dec. 10, 1971 now abandoned in favor of continuation application Ser. No 347,351, filed Apr. 2, 1973, and entitled "Apparatus For Impregnating Textile Fibers", the staple fibers which are essentially parallely disposed in the fiber arrangement are strongly compacted between work disks of the equipment. Swiss patent No. 541,361 corresponds to abandoned application Ser. No. 187,966. Still there cannot be avoided a certain expansion of the cross-section of the fiber arrangement departing from the work disks, which is dependent upon the fiber material, the degree of crimping of the fibers, the viscosity and nature of the liquid, the introduced liquid quantity or similar factors. Additionally, due to adhesion of the parallely oriented staple fibers at the periphery of the work disks the compactness of the still wet slubbing can further loosen. During drying of the wet slubbing by means of dry air it can be difficult to obtain yarn of sufficient breaking strength and sufficient surface smoothness.
A further drawback is the so-called "sandwich-effect" known to those skilled in the art which particularly occurs in the presence of hydrophilic staple fibers in the fiber arrangement. This sandwich-effect is brought about by virtue of the fact that with swelling of the fibers, which occurs after the introduction of the liquid, there occurs a migration of the liquid from for instance the external or outer cover layer towards the core of the slubbing and internally of the slubbing there is thus present a greater concentration of liquid. Of course, the adhesive distributed in the liquid is also effected thereby and after setting of the adhesive or drying there is obtained a yarn with only insufficient adhesively bonded cover or outer layer, i.e. a yarn possessing for instance a hairy appearance and correspondingly reduced breaking or tear strength. The sandwich-effect is particularly still further then intensified if it is simultaneously desired to maintain as short as possible the time between application of the liquid to the staple fibers and drying of the slubbing, whereby the dimensions of the installation can be desirably reduced.
Furthermore, with the known process it has been found by virtue of the previously discussed effect that the adhesion force of the adhesive distributed throughout the liquid can be only unsatisfactorily utilized, resulting in considerable economical drawbacks.